fw: replace straggler timer with per-strategy decision

remove onInterestReject pipeline

refs: #4200

Change-Id: I184d7ef7f732efda3d1066eef6cd89e36a6a8802

daemon/fw/forwarder.cpp

@@ -127,9 +127,6 @@ Forwarder::onIncomingInterest(Face& inFace, const Interest& interest)
     return;
   }
 
-  // cancel unsatisfy & straggler timer
-  this->cancelUnsatisfyAndStragglerTimer(*pitEntry);
-
   // is pending?
   if (!pitEntry->hasInRecords()) {
     m_cs.find(interest,
@@ -163,6 +160,12 @@ Forwarder::onInterestLoop(Face& inFace, const Interest& interest)
   inFace.sendNack(nack);
 }
 
+static inline bool
+compare_InRecord_expiry(const pit::InRecord& a, const pit::InRecord& b)
+{
+  return a.getExpiry() < b.getExpiry();
+}
+
 void
 Forwarder::onContentStoreMiss(const Face& inFace, const shared_ptr<pit::Entry>& pitEntry,
                               const Interest& interest)
@@ -173,8 +176,10 @@ Forwarder::onContentStoreMiss(const Face& inFace, const shared_ptr<pit::Entry>&
   // insert in-record
   pitEntry->insertOrUpdateInRecord(const_cast<Face&>(inFace), interest);
 
-  // set PIT unsatisfy timer
-  this->setUnsatisfyTimer(pitEntry);
+  // set PIT expiry timer to the time that the last PIT in-record expires
+  auto lastExpiring = std::max_element(pitEntry->in_begin(), pitEntry->in_end(), &compare_InRecord_expiry);
+  auto lastExpiryFromNow = lastExpiring->getExpiry() - time::steady_clock::now();
+  this->setExpiryTimer(pitEntry, time::duration_cast<time::milliseconds>(lastExpiryFromNow));
 
   // has NextHopFaceId?
   shared_ptr<lp::NextHopFaceIdTag> nextHopTag = interest.getTag<lp::NextHopFaceIdTag>();
@@ -208,8 +213,8 @@ Forwarder::onContentStoreHit(const Face& inFace, const shared_ptr<pit::Entry>& p
   pitEntry->isSatisfied = true;
   pitEntry->dataFreshnessPeriod = data.getFreshnessPeriod();
 
-  // set PIT straggler timer
-  this->setStragglerTimer(pitEntry);
+  // finalize Interest
+  this->onInterestFinalize(pitEntry);
 
   // goto outgoing Data pipeline
   this->onOutgoingData(data, *const_pointer_cast<Face>(inFace.shared_from_this()));
@@ -229,23 +234,6 @@ Forwarder::onOutgoingInterest(const shared_ptr<pit::Entry>& pitEntry, Face& outF
   ++m_counters.nOutInterests;
 }
 
-void
-Forwarder::onInterestReject(const shared_ptr<pit::Entry>& pitEntry)
-{
-  if (fw::hasPendingOutRecords(*pitEntry)) {
-    NFD_LOG_ERROR("onInterestReject interest=" << pitEntry->getName() <<
-                  " cannot reject forwarded Interest");
-    return;
-  }
-  NFD_LOG_DEBUG("onInterestReject interest=" << pitEntry->getName());
-
-  // cancel unsatisfy & straggler timer
-  this->cancelUnsatisfyAndStragglerTimer(*pitEntry);
-
-  // set PIT straggler timer
-  this->setStragglerTimer(pitEntry);
-}
-
 void
 Forwarder::onInterestFinalize(const shared_ptr<pit::Entry>& pitEntry)
 {
@@ -256,7 +244,7 @@ Forwarder::onInterestFinalize(const shared_ptr<pit::Entry>& pitEntry)
   this->insertDeadNonceList(*pitEntry, 0);
 
   // PIT delete
-  this->cancelUnsatisfyAndStragglerTimer(*pitEntry);
+  scheduler::cancel(pitEntry->expiryTimer);
   m_pit.erase(pitEntry.get());
 }
 
@@ -295,9 +283,6 @@ Forwarder::onIncomingData(Face& inFace, const Data& data)
   for (const shared_ptr<pit::Entry>& pitEntry : pitMatches) {
     NFD_LOG_DEBUG("onIncomingData matching=" << pitEntry->getName());
 
-    // cancel unsatisfy & straggler timer
-    this->cancelUnsatisfyAndStragglerTimer(*pitEntry);
-
     // remember pending downstreams
     for (const pit::InRecord& inRecord : pitEntry->getInRecords()) {
       if (inRecord.getExpiry() > now) {
@@ -305,6 +290,9 @@ Forwarder::onIncomingData(Face& inFace, const Data& data)
       }
     }
 
+    // set PIT expiry timer to now
+    this->setExpiryTimer(pitEntry, 0_ms);
+
     // invoke PIT satisfy callback
     this->dispatchToStrategy(*pitEntry,
       [&] (fw::Strategy& strategy) { strategy.beforeSatisfyInterest(pitEntry, inFace, data); });
@@ -318,9 +306,6 @@ Forwarder::onIncomingData(Face& inFace, const Data& data)
     // mark PIT satisfied
     pitEntry->clearInRecords();
     pitEntry->deleteOutRecord(inFace);
-
-    // set PIT straggler timer
-    this->setStragglerTimer(pitEntry);
   }
 
   // foreach pending downstream
@@ -426,6 +411,11 @@ Forwarder::onIncomingNack(Face& inFace, const lp::Nack& nack)
   // record Nack on out-record
   outRecord->setIncomingNack(nack);
 
+  // set PIT expiry timer to now when all out-record receive Nack
+  if (!fw::hasPendingOutRecords(*pitEntry)) {
+    this->setExpiryTimer(pitEntry, 0_ms);
+  }
+
   // trigger strategy: after receive NACK
   this->dispatchToStrategy(*pitEntry,
     [&] (fw::Strategy& strategy) { strategy.afterReceiveNack(inFace, nack, pitEntry); });
@@ -483,46 +473,17 @@ Forwarder::onDroppedInterest(Face& outFace, const Interest& interest)
   m_strategyChoice.findEffectiveStrategy(interest.getName()).onDroppedInterest(outFace, interest);
 }
 
-static inline bool
-compare_InRecord_expiry(const pit::InRecord& a, const pit::InRecord& b)
-{
-  return a.getExpiry() < b.getExpiry();
-}
-
 void
-Forwarder::setUnsatisfyTimer(const shared_ptr<pit::Entry>& pitEntry)
+Forwarder::setExpiryTimer(const shared_ptr<pit::Entry>& pitEntry, time::milliseconds duration)
 {
-  pit::InRecordCollection::iterator lastExpiring =
-    std::max_element(pitEntry->in_begin(), pitEntry->in_end(), &compare_InRecord_expiry);
+  BOOST_ASSERT(duration >= 0_ms);
 
-  time::steady_clock::TimePoint lastExpiry = lastExpiring->getExpiry();
-  time::nanoseconds lastExpiryFromNow = lastExpiry - time::steady_clock::now();
-  if (lastExpiryFromNow <= time::seconds::zero()) {
-    // TODO all in-records are already expired; will this happen?
-  }
+  scheduler::cancel(pitEntry->expiryTimer);
 
-  scheduler::cancel(pitEntry->m_unsatisfyTimer);
-  pitEntry->m_unsatisfyTimer = scheduler::schedule(lastExpiryFromNow,
+  pitEntry->expiryTimer = scheduler::schedule(duration,
     bind(&Forwarder::onInterestFinalize, this, pitEntry));
 }
 
-void
-Forwarder::setStragglerTimer(const shared_ptr<pit::Entry>& pitEntry)
-{
-  time::nanoseconds stragglerTime = time::milliseconds(100);
-
-  scheduler::cancel(pitEntry->m_stragglerTimer);
-  pitEntry->m_stragglerTimer = scheduler::schedule(stragglerTime,
-    bind(&Forwarder::onInterestFinalize, this, pitEntry));
-}
-
-void
-Forwarder::cancelUnsatisfyAndStragglerTimer(pit::Entry& pitEntry)
-{
-  scheduler::cancel(pitEntry.m_unsatisfyTimer);
-  scheduler::cancel(pitEntry.m_stragglerTimer);
-}
-
 static inline void
 insertNonceToDnl(DeadNonceList& dnl, const pit::Entry& pitEntry,
                  const pit::OutRecord& outRecord)

daemon/fw/forwarder.hpp

@@ -209,11 +209,6 @@ PUBLIC_WITH_TESTS_ELSE_PRIVATE: // pipelines
   VIRTUAL_WITH_TESTS void
   onOutgoingInterest(const shared_ptr<pit::Entry>& pitEntry, Face& outFace, const Interest& interest);
 
-  /** \brief Interest reject pipeline
-   */
-  VIRTUAL_WITH_TESTS void
-  onInterestReject(const shared_ptr<pit::Entry>& pitEntry);
-
   /** \brief Interest finalize pipeline
    */
   VIRTUAL_WITH_TESTS void
@@ -248,14 +243,10 @@ PUBLIC_WITH_TESTS_ELSE_PRIVATE: // pipelines
   onDroppedInterest(Face& outFace, const Interest& interest);
 
 PROTECTED_WITH_TESTS_ELSE_PRIVATE:
-  VIRTUAL_WITH_TESTS void
-  setUnsatisfyTimer(const shared_ptr<pit::Entry>& pitEntry);
-
-  VIRTUAL_WITH_TESTS void
-  setStragglerTimer(const shared_ptr<pit::Entry>& pitEntry);
-
-  VIRTUAL_WITH_TESTS void
-  cancelUnsatisfyAndStragglerTimer(pit::Entry& pitEntry);
+  /** \brief set a new expiry timer (now + \p duration) on a PIT entry
+   */
+  void
+  setExpiryTimer(const shared_ptr<pit::Entry>& pitEntry, time::milliseconds duration);
 
   /** \brief insert Nonce to Dead Nonce List if necessary
    *  \param upstream if null, insert Nonces from all out-records;

daemon/fw/strategy.hpp

@@ -121,11 +121,18 @@ public: // triggers
    *  - cannot be satisfied by ContentStore
    *  - is under a namespace managed by this strategy
    *
+   *  The PIT entry is set to expire after InterestLifetime has elapsed at each downstream.
+   *
    *  The strategy should decide whether and where to forward this Interest.
    *  - If the strategy decides to forward this Interest,
-   *    invoke this->sendInterest one or more times, either now or shortly after
-   *  - If strategy concludes that this Interest cannot be forwarded,
-   *    invoke this->rejectPendingInterest so that PIT entry will be deleted shortly
+   *    invoke \c sendInterest for each upstream, either now or shortly after via a scheduler event,
+   *    but before PIT entry expires.
+   *    Optionally, the strategy can invoke \c setExpiryTimer to adjust how long it would wait for a response.
+   *  - If the strategy has already forwarded this Interest previously and decides to continue waiting,
+   *    do nothing.
+   *    Optionally, the strategy can invoke \c setExpiryTimer to adjust how long it would wait for a response.
+   *  - If the strategy concludes that this Interest cannot be satisfied,
+   *    invoke \c rejectPendingInterest to erase the PIT entry.
    *
    *  \warning The strategy must not retain shared_ptr<pit::Entry>, otherwise undefined behavior
    *           may occur. However, the strategy is allowed to store weak_ptr<pit::Entry>.
@@ -137,7 +144,13 @@ public: // triggers
   /** \brief trigger before PIT entry is satisfied
    *
    *  This trigger is invoked when an incoming Data satisfies the PIT entry.
-   *  It can be invoked even if the PIT entry has already been satisfied.
+   *  Normally, only the first incoming Data would satisfy the PIT entry and invoke this trigger,
+   *  after which the PIT entry is erased.
+   *
+   *  If the strategy wishes to collect responses from additional upstream nodes,
+   *  it should invoke \c setExpiryTimer within this function to retain the PIT entry.
+   *  If a Data arrives from another upstream during the extended PIT entry lifetime, this trigger will be invoked again.
+   *  At that time, this function must invoke \c setExpiryTimer again to continue collecting more responses.
    *
    *  In this base class this method does nothing.
    *
@@ -156,6 +169,14 @@ public: // triggers
    *  to that upstream, i.e. the PIT out-record exists and has a matching Nonce.
    *  The NackHeader has been recorded in the PIT out-record.
    *
+   *  If the PIT entry is not yet satisfied, its expiry timer remains unchanged.
+   *  Otherwise, the PIT entry normally would expire immediately after this function returns.
+   *
+   *  If the strategy wishes to collect responses from additional upstream nodes,
+   *  it should invoke \c setExpiryTimer within this function to retain the PIT entry.
+   *  If a Nack arrives from another upstream during the extended PIT entry lifetime, this trigger will be invoked again.
+   *  At that time, this function must invoke \c setExpiryTimer again to continue collecting more responses.
+   *
    *  In this base class this method does nothing.
    *
    *  \warning The strategy must not retain shared_ptr<pit::Entry>, otherwise undefined behavior
@@ -185,16 +206,16 @@ protected: // actions
     m_forwarder.onOutgoingInterest(pitEntry, outFace, interest);
   }
 
-  /** \brief decide that a pending Interest cannot be forwarded
-   *  \param pitEntry PIT entry
+  /** \brief schedule the PIT entry for immediate deletion
    *
-   *  This shall not be called if the pending Interest has been
-   *  forwarded earlier, and does not need to be resent now.
+   *  This helper function sets the PIT entry expiry time to zero.
+   *  The strategy should invoke this function when it concludes that the Interest cannot
+   *  be forwarded and it does not want to wait for responses from existing upstream nodes.
    */
   VIRTUAL_WITH_TESTS void
   rejectPendingInterest(const shared_ptr<pit::Entry>& pitEntry)
   {
-    m_forwarder.onInterestReject(pitEntry);
+    this->setExpiryTimer(pitEntry, 0_ms);
   }
 
   /** \brief send Nack to outFace
@@ -222,6 +243,14 @@ protected: // actions
   sendNacks(const shared_ptr<pit::Entry>& pitEntry, const lp::NackHeader& header,
             std::initializer_list<const Face*> exceptFaces = std::initializer_list<const Face*>());
 
+  /** \brief Schedule the PIT entry to be erased after \p duration
+   */
+  void
+  setExpiryTimer(const shared_ptr<pit::Entry>& pitEntry, time::milliseconds duration)
+  {
+    m_forwarder.setExpiryTimer(pitEntry, duration);
+  }
+
 protected: // accessors
   /** \brief performs a FIB lookup, considering Link object if present
    */

daemon/table/pit-entry.hpp

@@ -215,26 +215,11 @@ public: // out-record
   deleteOutRecord(const Face& face);
 
 public:
-  /** \brief unsatisfy timer
+  /** \brief expiry timer
    *
    *  This timer is used in forwarding pipelines to delete the entry
-   *  when it expires without being satisfied.
-   *  It fires when the last InterestLifetime among in-records expires.
-   *
-   *  Either this or the straggler timer should be set at all times,
-   *  except when this entry is being processed in a pipeline.
    */
-  scheduler::EventId m_unsatisfyTimer;
-
-  /** \brief straggler timer
-   *
-   *  This timer is used in forwarding pipelines to delete the entry when it has been satisfied
-   *  and is no longer needed for measurement collection purpose.
-   *
-   *  Either this or the unsatisfy timer should be set at all times,
-   *  except when this entry is being processed in a pipeline.
-   */
-  scheduler::EventId m_stragglerTimer;
+  scheduler::EventId expiryTimer;
 
   /** \brief indicate if PIT entry is satisfied
    */

tests/daemon/fw/pit-expiry.t.cpp

@@ -0,0 +1,284 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2014-2018,  Regents of the University of California,
+ *                           Arizona Board of Regents,
+ *                           Colorado State University,
+ *                           University Pierre & Marie Curie, Sorbonne University,
+ *                           Washington University in St. Louis,
+ *                           Beijing Institute of Technology,
+ *                           The University of Memphis.
+ *
+ * This file is part of NFD (Named Data Networking Forwarding Daemon).
+ * See AUTHORS.md for complete list of NFD authors and contributors.
+ *
+ * NFD is free software: you can redistribute it and/or modify it under the terms
+ * of the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * NFD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+ * PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * NFD, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "dummy-strategy.hpp"
+#include "choose-strategy.hpp"
+#include "tests/daemon/face/dummy-face.hpp"
+
+#include "tests/test-common.hpp"
+
+namespace nfd {
+namespace fw {
+namespace tests {
+
+using namespace nfd::tests;
+
+BOOST_AUTO_TEST_SUITE(Fw)
+BOOST_FIXTURE_TEST_SUITE(TestPitExpiry, UnitTestTimeFixture)
+
+class PitExpiryTestStrategy : public DummyStrategy
+{
+public:
+  static Name
+  getStrategyName(uint64_t version)
+  {
+    return Name("/PitExpiryTestStrategy").appendVersion(version);
+  }
+
+  static void
+  registerAs(const Name& strategyName)
+  {
+    registerAsImpl<PitExpiryTestStrategy>(strategyName);
+  }
+
+  explicit
+  PitExpiryTestStrategy(Forwarder& forwarder, const Name& name = getStrategyName(1))
+    : DummyStrategy(forwarder, name)
+  {
+  }
+
+  void
+  afterReceiveInterest(const Face& inFace, const Interest& interest,
+                       const shared_ptr<pit::Entry>& pitEntry) override
+  {
+    ++afterReceiveInterest_count;
+
+    if (afterReceiveInterest_count <= 1) {
+      setExpiryTimer(pitEntry, 190_ms);
+    }
+  }
+
+  void
+  beforeSatisfyInterest(const shared_ptr<pit::Entry>& pitEntry,
+                        const Face& inFace, const Data& data) override
+  {
+    ++beforeSatisfyInterest_count;
+
+    if (beforeSatisfyInterest_count <= 1 ) {
+      setExpiryTimer(pitEntry, 190_ms);
+    }
+  }
+
+  void
+  afterReceiveNack(const Face& inFace, const lp::Nack& nack,
+                   const shared_ptr<pit::Entry>& pitEntry) override
+  {
+    ++afterReceiveNack_count;
+
+    if (afterReceiveNack_count <= 1) {
+      setExpiryTimer(pitEntry, 50_ms);
+    }
+  }
+};
+
+BOOST_AUTO_TEST_CASE(UnsatisfiedInterest)
+{
+  Forwarder forwarder;
+
+  auto face1 = make_shared<DummyFace>();
+  auto face2 = make_shared<DummyFace>();
+  forwarder.addFace(face1);
+  forwarder.addFace(face2);
+
+  Pit& pit = forwarder.getPit();
+
+  shared_ptr<Interest> interest1 = makeInterest("/A/0");
+  shared_ptr<Interest> interest2 = makeInterest("/A/1");
+  interest1->setInterestLifetime(90_ms);
+  interest2->setInterestLifetime(90_ms);
+
+  face1->receiveInterest(*interest1);
+  face2->receiveInterest(*interest2);
+  BOOST_CHECK_EQUAL(pit.size(), 2);
+
+  this->advanceClocks(100_ms);
+  BOOST_CHECK_EQUAL(pit.size(), 0);
+}
+
+BOOST_AUTO_TEST_CASE(SatisfiedInterest)
+{
+  Forwarder forwarder;
+
+  auto face1 = make_shared<DummyFace>();
+  auto face2 = make_shared<DummyFace>();
+  forwarder.addFace(face1);
+  forwarder.addFace(face2);
+
+  Pit& pit = forwarder.getPit();
+
+  shared_ptr<Interest> interest = makeInterest("/A/0");
+  interest->setInterestLifetime(90_ms);
+  shared_ptr<Data> data = makeData("/A/0");
+
+  face1->receiveInterest(*interest);
+
+  this->advanceClocks(30_ms);
+  face2->receiveData(*data);
+
+  this->advanceClocks(1_ms);
+  BOOST_CHECK_EQUAL(pit.size(), 0);
+}
+
+BOOST_AUTO_TEST_CASE(ReceiveNack)
+{
+  Forwarder forwarder;
+
+  auto face1 = make_shared<DummyFace>();
+  auto face2 = make_shared<DummyFace>();
+  auto face3 = make_shared<DummyFace>();
+  forwarder.addFace(face1);
+  forwarder.addFace(face2);
+  forwarder.addFace(face3);
+
+  Name strategyA("/strategyA/%FD%01");
+  PitExpiryTestStrategy::registerAs(strategyA);
+  choose<PitExpiryTestStrategy>(forwarder, "/A", strategyA);
+
+  Pit& pit = forwarder.getPit();
+
+  shared_ptr<Interest> interest = makeInterest("/A/0", 562);
+  interest->setInterestLifetime(90_ms);
+  lp::Nack nack = makeNack("/A/0", 562, lp::NackReason::CONGESTION);
+
+  face1->receiveInterest(*interest);
+  auto entry = pit.find(*interest);
+  entry->insertOrUpdateOutRecord(*face2, *interest);
+  entry->insertOrUpdateOutRecord(*face3, *interest);
+
+  this->advanceClocks(10_ms);
+  face2->receiveNack(nack);
+
+  this->advanceClocks(1_ms);
+  BOOST_CHECK_EQUAL(pit.size(), 1);
+
+  this->advanceClocks(50_ms);
+  BOOST_CHECK_EQUAL(pit.size(), 0);
+}
+
+BOOST_AUTO_TEST_CASE(ResetTimerAfterReceiveInterest)
+{
+  Forwarder forwarder;
+
+  auto face = make_shared<DummyFace>();
+  forwarder.addFace(face);
+
+  Name strategyA("/strategyA/%FD%01");
+  PitExpiryTestStrategy::registerAs(strategyA);
+  choose<PitExpiryTestStrategy>(forwarder, "/A", strategyA);
+
+  Pit& pit = forwarder.getPit();
+
+  shared_ptr<Interest> interest = makeInterest("/A/0");
+  interest->setInterestLifetime(90_ms);
+
+  face->receiveInterest(*interest);
+  BOOST_CHECK_EQUAL(pit.size(), 1);
+
+  this->advanceClocks(100_ms);
+  BOOST_CHECK_EQUAL(pit.size(), 1);
+
+  this->advanceClocks(100_ms);
+  BOOST_CHECK_EQUAL(pit.size(), 0);
+}
+
+BOOST_AUTO_TEST_CASE(ResetTimerBeforeSatisfyInterest)
+{
+  Forwarder forwarder;
+
+  auto face1 = make_shared<DummyFace>();
+  auto face2 = make_shared<DummyFace>();
+  forwarder.addFace(face1);
+  forwarder.addFace(face2);
+
+  Name strategyA("/strategyA/%FD%01");
+  PitExpiryTestStrategy::registerAs(strategyA);
+  choose<PitExpiryTestStrategy>(forwarder, "/A", strategyA);
+
+  Pit& pit = forwarder.getPit();
+
+  shared_ptr<Interest> interest = makeInterest("/A/0");
+  interest->setInterestLifetime(90_ms);
+  shared_ptr<Data> data = makeData("/A/0");
+
+  face1->receiveInterest(*interest);
+
+  this->advanceClocks(30_ms);
+  face2->receiveData(*data);
+
+  this->advanceClocks(1_ms);
+  BOOST_CHECK_EQUAL(pit.size(), 1);
+
+  this->advanceClocks(30_ms);
+  face2->receiveData(*data);
+
+  this->advanceClocks(1_ms);
+  BOOST_CHECK_EQUAL(pit.size(), 0);
+}
+
+BOOST_AUTO_TEST_CASE(ReceiveNackAfterResetTimer)
+{
+  Forwarder forwarder;
+
+  auto face1 = make_shared<DummyFace>();
+  auto face2 = make_shared<DummyFace>();
+  auto face3 = make_shared<DummyFace>();
+  forwarder.addFace(face1);
+  forwarder.addFace(face2);
+  forwarder.addFace(face3);
+
+  Name strategyA("/strategyA/%FD%01");
+  PitExpiryTestStrategy::registerAs(strategyA);
+  choose<PitExpiryTestStrategy>(forwarder, "/A", strategyA);
+
+  Pit& pit = forwarder.getPit();
+
+  shared_ptr<Interest> interest = makeInterest("/A/0", 562);
+  interest->setInterestLifetime(90_ms);
+  lp::Nack nack = makeNack("/A/0", 562, lp::NackReason::CONGESTION);
+
+  face1->receiveInterest(*interest);
+  auto entry = pit.find(*interest);
+  entry->insertOrUpdateOutRecord(*face2, *interest);
+  entry->insertOrUpdateOutRecord(*face3, *interest);
+
+  //pitEntry is not erased after receiving the first Nack
+  this->advanceClocks(10_ms);
+  face2->receiveNack(nack);
+  this->advanceClocks(1_ms);
+  BOOST_CHECK_EQUAL(pit.size(), 1);
+
+  //pitEntry is erased after receiving the second Nack
+  this->advanceClocks(10_ms);
+  face3->receiveNack(nack);
+  this->advanceClocks(1_ms);
+  BOOST_CHECK_EQUAL(pit.size(), 0);
+}
+
+BOOST_AUTO_TEST_SUITE_END() // TestPitExpiry
+BOOST_AUTO_TEST_SUITE_END() // Fw
+
+} // namespace tests
+} // namespace fw
+} // namespace nfd